1. Field of the Invention
The present invention relates to locking mechanisms for door locks in which the handle is allowed to "free-wheel", i.e., rotate without retracting the latchbolt, when the mechanism is locked. More particularly, this invention relates to locking mechanisms of the type which are provided with a handle and mounted to the exterior face of a door to operate a latching mechanism mounted inside the door.
2. Description of Related Art
One type of door lock that is widely used in public buildings, businesses, schools and the like includes a latching mechanism (door latch) mounted inside the door and inner and outer handle mechanisms or trim sets which operate the latching mechanism. The latching mechanism includes one or more latches which hold the door to the door frame. The inner and outer handle mechanisms are surface mounted on the inner and outer faces of the door and operate the latching mechanism inside the door.
The latches may be conventional vertical rod latches extending out the top and/or bottom edge of the door, or a single conventional center latch bolt may extend out the edge of the door. Regardless of the particulars of the latching mechanism, however, it will include a central operating point, to which the externally mounted handle mechanisms will attach, commonly through a shaft which rotates to operate the latching mechanism. The central operating point retracts the latch bolt and/or latch rods out of latching engagement with the door frame when a handle on the inner or outer handle mechanism is turned.
The inner and outer handle mechanisms are each provided with a handle which may be rotated to retract the latches and open the door. Each handle mechanism is provided with a spindle or shaft that extends from the handle mechanism through the surface of the door and into the central operating point of the latching mechanism.
In one popular implementation of this basic type of door lock, the outer handle mechanism houses the locking mechanism and includes all the locking components necessary to lock the door, in addition to the handle and basic case in which they are mounted. The function of the locking mechanism in this type of design is to prevent the handle shaft from turning whenever the locking mechanism is locked, and thereby prevent the door from being opened. The outer handle mechanism with its integrated locking functionality may then be attached to any desired type of door latch, and the latching mechanism need not have any means of being locked.
Up to now, in devices of this type the handle has been connected substantially directly to the latching mechanism, most often through a solid shaft, and the locking function has been achieved by physically blocking the motion of the handle, the shaft or components connected thereto. The rotation of the handle or shaft is blocked when the door is locked by turning a key in the locking mechanism. This has been a highly successful design when the handle is a conventional door knob. However, the advent of lever handles has increased the lock requirements greatly and made it very difficult to adequately strengthen internal lock components to withstand the forces that can be applied to prevent a lever handle from being turned. The outer handle and lock mechanism, when provided with a lever handle may be referred to as a lever handle controller, and the present invention generally relates to such devices.
Doors are much easier to open when the handle is shaped as a lever rather than a conventional round door knob. For this reason, lever handles are preferred in some applications, and they may be required under applicable regulations for certain doors in public buildings to facilitate access by the disabled and the elderly.
However, the lever shape of the door handle allows a large force to be applied to the locking mechanism of the door and to the mounting between the door and the locking mechanism. The greater leverage available from a lever handle may allow a vandal or thief to break the internal components of the door lock by standing or jumping on the lever end of the handle.
To address this problem, the present invention has been designed such that the handle on the locking mechanism is disengaged from the shaft extending from the locking mechanism to the latching mechanism. This allows the handle to free-wheel or rotate without operating the latching mechanism and prevents the lever handle from being used to overstress the components of the door lock. Free-wheeling surface mounted lock mechanisms for controlling separate latch mechanisms have not heretofore been available.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a lock mechanism for operating a door latch which allows the handle to free-wheel when the door is locked.
It is another object of the present invention to provide a free-wheeling lock mechanism in which the connection between the handle and shaft extending to operate the door latch is both rugged and reliable, yet relatively inexpensive, the connection allowing a relatively high level of torque-to be transmitted through to the door latch from the handle when the door is unlocked and yet being disengageable when the door is locked to provide for free-wheeling operation.
Yet another object of the present invention to provide a free-wheeling lock mechanism in which the mechanism shifts positively and completely from the fully locked to the fully unlocked position.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.